AM Fungi Inoculation Relieves Cadmium Stress On Tobacco Seedlings In Mineral Absorption And Vegetative Growth As Well As Physiological Metabolization

Arbuscular mycorrhizal fungi(AMF)can improve plant toxicity against heavy metals.The aim of this study was to evaluate the effect of AMF on tobacco growth and Cd toxicity under Cd stress.Tobacco,as one of the important economic crops in China,has a very important social and economic role.However,soil cadmium affects the seed germination,tobacco development,apparent morphology,photosynthesis and enzyme activity of tobacco through various pathways.Cadmium pollution is the most polluted area in China,the most serious pollution of a typical form of heavy metal pollution.Tobacco plants with high levels of heavy metals are not only affected by their growth and yield,but also the quality of tobacco leaves will be significantly reduced.With the growing concern about "smoking and health",tobacco safety issues are getting more and more attention.The study of the relationship between tobacco and heavy metals has become one of the hot spots of tobacco research at home and abroad.Tobacco harmful heavy metal components are arsenic(As),cadmium(Cd),chromium(Cr),mercury(Hg)and lead(Pb).Cd and Pb are likely to be the main heavy metal elements in China's flue-cured tobacco leaves.Cd is the main heavy metal element in tobacco leaves.Tobacco has strong ability to enrich Cd,followed by Hg,and the enrichment ability of Pb,Cr and As is relatively weak.Cadmium stress not only causes sugar,chlorophyll and protein synthesis to be blocked,but also can cause photosynthetic intensity and respiratory strength decreased,carbohydrate metabolic disorders and a series of other physiological metabolic disorders,thereby hindering plant root growth,affecting seed germination,plant growth,Growth and yield decline,and even lead to plant death.The activities of AMF in soil affected the rhizosphere environment of tobacco,and rhizosphere environment affected the species and reproduction of rhizosphere microorganisms,which affected the absorption of nutrients.Under the condition of adversity,arbuscular mycorrhiza mainly improves the nutrient status of plants and improves the soil structure by expanding the range of root absorption and activating soil nutrients,so as to improve the salt tolerance,acid resistance,cold resistance and heavy metal toxicity Wait.Many studies have found that AMF can directly and indirectly affect the plant on the soil of heavy metal elements in the absorption and accumulation,and thus affect the toxic effects of heavy metal pollution on plants.In order to further explore the effects of AMF on tobacco stress and cadmium resistance under the condition of cadmium stress,three factors were set up: AMF,AMF and simulated cadmium stress were inoculated.In the plug floating seedling,the matrix and water without Cd treatment,indoor culture for 1 month,obtained asylum healthy tobacco seedlings.During the preparation of Cd stress test matrix.When preparing the substrate,weighed Cr(NO3)2 · 4H2 O,dissolved in a 1 L distilled glass container,poured into a stirred plastic box containing a sterile matrix,and each was well mixed to obtain different concentrations of Cd treatment of soil.Approximately 2.5kg of soil is treated in each test bowl.When the tobacco leaves the fifth leaf in the floating basin,the test began,and the five-leaf-age non-myrtle tobacco seedlings of the same size were transplanted into the test bowl.In the inoculation treatment,100 g of the bacterial seed was added to each seedling in the single inoculation treatment.However,50 g each of each fungicide was added with 100 g of the bacterial agent for AMF inoculation.The AMF treatment was not inoculated with 100 g Sterilized bacteria.Each treatment was repeated 5 times,and the smoky seedlings were transplanted by 1 plant / bowl.The treated tobacco seedlings were placed in a greenhouse at 25?-28?.During the day,the photosynthesis was carried out in the daytime.The animals were incubated for 120 days and the indexes were measured for 120 days.The main results are as follows:(1)Heavy metal Cd effect on the growth and physiological metabolism of tobacco seedlings showed low and high dose effectCompared with the control group(Cd concentration 0mg/kg),the photosynthetic indexes,the contents of osmotic adjustment and the activity of leaf protective enzymes were significantly increased when the Cd concentration was 5mg/kg,The results showed that low concentration(5mg/kg)cadmium could promote plant growth.When Cd concentration increased to 20mg/kg and 40mg/kg,the growth of tobacco seedlings was inhibited gradually,and the photosynthetic indexes,photosynthetic physiological indexes The activity of leaf was significantly lower than that of the control group.It can be seen that Cd ions can promote the growth and resistance index of tobacco plants under low concentration,and will significantly inhibit the growth and resistance of tobacco plants under high concentration,and have obvious low and high dose effect.Cadmium mainly accumulated in the tobacco,followed by the root,the stem content of the lowest.(2)Under the condition of Cd stress,AMF and tobacco were able to form mycorrhizal symbiosisInfection rate is an indicator of mycorrhizal and symbiotic fungi on plant affinity.Under the condition of Cd stress,the inoculation of AMF could effectively infect the tobacco root.In the cadmium concentration gradient,the increase of cadmium content had obvious effect on the infection rate.In the 5mg/kg Cd concentration treatment,different AMF The highest levels of mycorrhizal infection were observed.Although the mycorrhizal infection rate began to decrease with the increase in Cd concentration(>5mg/kg,<40mg/kg),the infection rate was still higher than 10%.And the Cd resistance of double-inoculated AMF treatment was higher than that of single inoculation.In the single inoculation,the symbiosis effect of Moxi globulin and tobacco was better.It is suggested that the symbiosis of mycorrhizal fungi can be formed by the amphoteric fungi and the tobacco seedlings.The AMF can form symbiosis system with the tobacco.(3)AMF can reduce the harm of tobacco seedlings under Cd stressIn the range of 0-40mg/kg Cd concentration,the nutrient growth index,photosynthetic physiological indexes,osmotic adjustment were observed in the treatment of the same Cd concentration.The content of leaf and the protective enzyme activity of the leaves were higher than those of the non-inoculated tobacco seedlings and the same bacteria under different cadmium concentration.When the Cd concentration was 5mg/kg,the anti-stress ability was the most prominent,Stress tolerance and metabolic levels under stress.Therefore,AMF is a kind of symbiotic beneficial bacteria that tobacco responds to Cd stress.Inoculation of AMF can reduce the harm of cadmium stress to tobacco seedlings,(4)Double-inoculated AMF tobacco K326 anti-cadmium capacity greater than single inoculation.Arbuscular mycorrhizal fungi are symbiotic beneficial bacteria controlled by tobacco Cd levels,and there are a variety of AMF interactions in nature affecting plant growth.In this study,it was found that the treatment of single inoculation of Rhodocephalus moniliforme,Rhizoctonia,Methionine and Lymphocystis and Methanocysts could be used to form a good Mycorrhizal symbiotic relationship,can significantly promote the growth of tobacco seedlings,light and physiological indicators,osmotic adjustment substances,leaf protective enzyme activity.Compared with single inoculation of AMF,double inoculation effect is better.The double inoculation of tobacco under Cd stress could reduce the damage of photosynthesis,improve the content of osmotic adjustment substance and maintain high protective enzyme activity.It can be seen that arbuscular mycorrhizal fungi have certain resistance to cadmium stress.The effect of double inoculation of arbuscular mycorrhizal fungi on tobacco growth and cadmium stress was better.